Power unit for motorcycle

Abstract

A power unit for a motorcycle includes an internal combustion engine provided with a crankcase rotatably supporting a crankshaft with an axial line extending in a vehicle-width direction. An oil pump is mounted on the crankcase with a balancer rotatably supported by the crankcase. Rotational power from the crankshaft is transmitted to a pump driven member provided on a pump shall of the oil pump and to a balancer driven member coaxially interlinked with and connected to the balancer so as to transmit power to the balancer. The power unit is downsized by bringing a balancer and an oil pump into a close arrangement. The pump driven member and the balancer driven member are offset from each other in a vehicle-width direction and are located at such a position so as to at least partially overlap each other as viewed from the side of the vehicle-width direction.

1. A power unit for a motorcycle, comprising:
 an internal combustion engine provided with a crankcase rotatably supporting a crankshaft with an axial line extending in a vehicle-width direction; and 
 a power transmission device for changing and reducing the speed of rotational power from the crankshaft and transmitting the resulting rotational power to a rear wheel; 
 wherein an oil pump for supplying oil to lubricating portions of the internal combustion engine is mounted on the crankcase and a balancer is rotatably supported by the crankcase; 
 wherein rotational power from the crankshaft is transmitted to a pump driven member provided on a pump shaft of the oil pump and to a balancer driven member coaxially interlinked with and connected to the balancer so as to transmit power to the balancer; and 
 wherein the pump driven member and the balancer driven member are offset from each other in a vehicle-width direction and are located at such a position so as to at least partially overlap each other as viewed from the side of the vehicle-width direction. 
 
     
     
       2. The power unit for a motorcycle according to  claim 1 , wherein an axial line of the pump shaft, an axial line of the balancer, and the axial line of the crankshaft are each disposed at a corresponding one of apexes of an imaginary triangle with the axial line of the crankshaft located at an upper apex thereof in a view projected on a plane perpendicular to the axial line of the crankshaft. 
     
     
       3. The power unit for a motorcycle according to  claim 2 , wherein the axial line of the pump shaft and then axial line of the balancer are disposed in front or rear of a vertical line passing the axial line of the crankshaft. 
     
     
       4. The power unit for a motorcycle according to  claim 2 ,
 wherein the power transmission device is disposed rearward of the crankshaft, the power transmission device including a continuously variable transmission having a belt wound around a drive pulley receiving power transmitted from the crankshaft thereto and around a driven pulley; and 
 wherein the drive pulley and the driven pulley are arranged one above the other so that a first straight line is parallel to a second straight line on the view projected on the plane, the first straight line connecting the respective axial lines of the drive pulley and the driven pulley, the second straight line connecting the axial line of the crankshaft with an axial line disposed rearward of the vertical line passing the axial line of the crankshaft, of the axial line of the pump shaft and the axial line of the balancer. 
 
     
     
       5. The power unit for a motorcycle according to  claim 3 ,
 wherein the power transmission device is disposed rearward of the crankshaft, the power transmission device including a continuously variable transmission having a belt wound around a drive pulley receiving power transmitted from the crankshaft thereto and around a driven pulley; and 
 wherein the drive pulley and the driven pulley are arranged one above the other so that a first straight line is parallel to a second straight line on the view projected on the plane, the first straight line connecting the respective axial lines of the drive pulley and the driven pulley, the second straight line connecting the axial line of the crankshaft with an axial line disposed rearward of the vertical line passing the axial line of the crankshaft, of the axial line of the pump shaft and the axial line of the balancer. 
 
     
     
       6. The power unit for a motorcycle according to  claim 1 , wherein the balancer coaxially surrounds a balancer shaft positioned between a fourth journal wall and a fifth journal wall with a pair of needle bearings interposed between the balancer shaft and the balancer for axially spacing each other apart. 
     
     
       7. The power unit for a motorcycle according to  claim 2 , wherein the axial line of the pump shaft is located forward of a second vertical line and the axial line of the balancer is located rearward of the second vertical line. 
     
     
       8. The power unit for a motorcycle according to  claim 1 , wherein a driven sprocket on the pump shaft of the oil pump and a driven gear of the balancer are offset from each other in the vehicle-width direction for reducing a misalignment of the oil pump and the balancer within the crankcase for reducing the size of the power unit. 
     
     
       9. The power unit for a motorcycle according to  claim 2 , wherein a drive pulley and a driven pulley of a continuously variable transmission are disposed rearward of the crankshaft with the axial line of the pump shaft being disposed rearward of a second line of the axial line of the pump shaft and an axial line of the balancer. 
     
     
       10. The power unit for a motorcycle according to  claim 1 , and further including an oil pan joined to the crankcase with an internal partitioning for storing a first oil for the internal combustion engine and a second oil for a continuously variable transmission. 
     
     
       11. A power unit, comprising:
 an internal combustion engine having a crankcase rotatably supporting a crankshaft with an axial line extending in a vehicle-width direction; 
 a power transmission device operatively connected to the crankshaft for changing and reducing the speed of rotational power from the crankshaft; 
 an oil pump for supplying oil to lubricating portions of the internal combustion engine, said oil pump being mounted on the crankcase; 
 a balancer rotatably supported by the crankcase; 
 wherein rotational power from the crankshaft is transmitted to a pump driven member provided on a pump shaft of the oil pump and to a balancer driven member coaxially interlinked with and connected to the balancer so as to transmit power to the balancer; and 
 wherein the pump driven member and the balancer driven member are offset from each other in a vehicle-width direction and are located at such a position so as to at least partially overlap each other as viewed from the side of the vehicle-width direction. 
 
     
     
       12. The power unit according to  claim 11 , wherein an axial line of the pump shaft, an axial line of the balancer, and the axial line of the crankshaft are each disposed at a corresponding one of apexes of an imaginary triangle with the axial line of the crankshaft located at an upper apex thereof in a view projected on a plane perpendicular to the axial line of the crankshaft. 
     
     
       13. The power unit according to  claim 12 , wherein the axial line of the pump shaft and then axial line of the balancer are disposed in front or rear of a vertical line passing the axial line of the crankshaft. 
     
     
       14. The power unit according to  claim 12 ,
 wherein the power transmission device is disposed rearward of the crankshaft, the power transmission device including a continuously variable transmission having a belt wound around a drive pulley receiving power transmitted from the crankshaft thereto and around a driven pulley; and 
 wherein the drive pulley and the driven pulley are arranged one above the other so that a first straight line is parallel to a second straight line on the view projected on the plane, the first straight line connecting the respective axial lines of the drive pulley and the driven pulley, the second straight line connecting the axial line of the crankshaft with an axial line disposed rearward of the vertical line passing the axial line of the crankshaft, of the axial line of the pump shaft and the axial line of the balancer. 
 
     
     
       15. The power unit according to  claim 13 ,
 wherein the power transmission device is disposed rearward of the crankshaft, the power transmission device including a continuously variable transmission having a belt wound around a drive pulley receiving power transmitted from the crankshaft thereto and around a driven pulley; and 
 wherein the drive pulley and the driven pulley are arranged one above the other so that a first straight line is parallel to a second straight line on the view projected on the plane, the first straight line connecting the respective axial lines of the drive pulley and the driven pulley, the second straight line connecting the axial line of the crankshaft with an axial line disposed rearward of the vertical line passing the axial line of the crankshaft, of the axial line of the pump shaft and the axial line of the balancer. 
 
     
     
       16. The power unit according to  claim 11 , wherein the balancer coaxially surrounds a balancer shaft positioned between a fourth journal wall and a fifth journal wall with a pair of needle bearings interposed between the balancer shaft and the balancer for axially spacing each other apart. 
     
     
       17. The power unit according to  claim 12 , wherein the axial line of the pump shaft is located forward of a second vertical line and the axial line of the balancer is located rearward of the second vertical line. 
     
     
       18. The power unit according to  claim 11 , wherein a driven sprocket on the pump shaft of the oil pump and a driven gear of the balancer are offset from each other in the vehicle-width direction for reducing a misalignment of the oil pump and the balancer within the crankcase for reducing the size of the power unit. 
     
     
       19. The power unit according to  claim 12 , wherein a drive pulley and a driven pulley of a continuously variable transmission are disposed rearward of the crankshaft with the axial line of the pump shaft being disposed rearward of a second line of the axial line of the pump shaft and an axial line of the balancer. 
     
     
       20. The power unit according to  claim 11 , and further including an oil pan joined to the crankcase with an internal partitioning for storing a first oil for the internal combustion engine and a second oil for a continuously variable transmission.